This invention relates to a method of detecting the presence of a conductive fluid in a chamber and apparatus for carrying out the method. One application of the invention is to provide a warning of the presence of water or other conductive coolant fluid in the oil in the oil pan of an internal combustion engine.
In the past, a variety of methods and apparatus which detect changes in conductivity have been used for this purpose. However, in addition to having other disadvantages, they have been found to be unacceptably susceptible to malfunction as a result of the build up of sludge over a prolonged period of time. This sludge which forms from contaminants in the lubricating oil has an insulative effect which may prevent the flow of current, despite the presence of conductive coolant fluid. U.S. Pat. No. 2,716,165 to Pfitzner which issued Aug. 23, 1955 shows a structure with a sensor probe received in a special housing in the oil pan or crank case of the engine. In addition to the insulative sludge from the lubricating oil which builds up on the electrodes over a period of time, this structure has the disadvantage that is prohibitively expensive to install, particularly on existing engines. U.S. Pat. No. 4,030,028 to Allender which issued June 14, 1977 shows a sensor which is mounted in place of the oil drain plug, but this structure has the disadvantage that the sensor is not located right at the bottom of the oil pan, as well as also being susceptible to the build up of insulative sludge which settles out of the oil onto the sensor. U.S. Pat. No. 3,793,586 to Heeps which issued Feb. 19, 1974 relates to a water detector for aircraft fuel tanks which utilizes a depending electrode structure. However, this structure is not satisfactory for use in an oil pan because of the problem of the build up of insulative sludge from the oil.